Beidou is an Electro type claymore user, and can be considered as a “tank”. Her elemental skill is her main unique point. You can hold the skill down to enter a guard stance that absorbs some damage taken and unleashes it in a wide area upon release. This skill can deal HIGH damage, and you only need to block at least 2 attacks, or just 1 if you ascend her once and time your block. The shield value itself is pretty decent, but it won't block status effects (blocking attacks that can freeze you will end up cancelling the damage part). Her elemental burst costs 80 energy, which is quite high, but it's an amazing ability to deal damage against groups of enemies, and good for causing elemental reactions.
If you want her to become your main damage dealer, then it's recommended to focus on her physical damage. At early to mid levels (1~50/60), you can use a somewhat cheap and easy to build artifact sets by using 2 piece Gladiators Finale with 2 piece Resolution of Sojourner or Brave Heart for an easy attack increase. At later levels, you can start to aim for 5 star gladiator pieces, and use 2 piece Bloodstained Chivalry to go with the gladiator. Use physical damage increase% as your mainstat on your artifact cup, and crit rate main stat on your crown piece if you don't have a weapon with a crit rate as the secondary.
The best weapon that you can give to her is the Wolfs Gravestone, but any other 5 star weapons can be a good substitute due to their higher base attack and strong passives. If you don't have any of the five stars, Serpent Spine can be a pretty good option because it gives crit rate as the secondary, and has the potential to deal very high damage, but it has its risks. For a safer playstyle, Prototype Aminus is a really good and strong F2P weapon that is generally good on most claymore damage dealers.
If you only bring her on the team to use her elemental skill, you will benefit more by focusing on Electro damage bonuses. Use 2 piece Thundering Fury, with 2 piece Gladiators, or 4 piece Thundersoother for higher damage on her elemental burst, but this is only if you don't plan on playing with elemental reactions, or paired with Hydro damage dealers only.
Any high attack weapon for damage dealers will still be good for her, but for a more support type weapon, you can use Sacrificial Greatsword, giving you a chance of being able to use her elemental skill twice. There's also The Bell for higher survivability.
As a support, you can pretty much bring her to any team and she will still be just as useful. But if you want to build a team around her because you build her for damage dealer role, pair her up with Xingqiu for constant Electro-Charged reaction when you use their elemental bursts, or Kaeya/Qiqi for Superconduct so your normal attacks deal more damage. If you want a Pyro unit for Overloaded reaction, you can use Bennett, who is also a pretty strong and effective healer.
Nothing to worry about. Should anyone raise a hand against her or her men, she will avenge it ten-fold with sword and thunder.
Press Accumulating the power of lightning, Beidou swings her blade forward fiercely, dealing Electro DMG.
Hold Lifts her weapon up as a shield. Max DMG absorbed scales off Beidou's Max HP.
Attacks using the energy stored within the greatsword upon release or once this ability's duration expires, dealing Electro DMG. DMG dealt scales with the number of times Beidou is attacked in the skill's duration. The greatest DMG Bonus will be attained once this effect is triggered twice.
The shield possesses the following properties:
Has 250% Electro DMG Absorption Efficiency.
Applies the Electro element to Beidou upon activation.
Recalling her slaying of the great beast Haishan. Beidou calls upon that monstrous strength and the lightning to create a Thunderbeast's Targe around herself.
When Normal and Charged Attacks hit, they create a lightning discharge that can jump between enemies, dealing Electro DMG.
Increases the character's resistance to interruption, and decreases DMG taken.
Counterattacking with Tidecaller at the precise moment when the character is hit grants the maximum DMG Bonus.
Gain the following effects for 10s after unleashing Tidecaller with its maximum DMG Bonus: - DMG dealt by Normal and Charged Attacks is increased by 15%. ATK SPD of Normal and Charged Attacks is increased by 15%. -Greatly reduced delay before unleashing Charged Attacks.
Conqueror of Tides
Decreases all party member's swimming Stamina consumption by 20%.